Low viscosity defoaming/antiforming formulations

The polypropylene glycols and polyoxyethylene-polyoxypropylene copolymers which have been employed individually as antifoaming agents have several drawbacks. Primarily, they have limited water solubility and dispersibility so that large amounts of these antifoamers must be employed and, even then, the defoaming action is relatively low. Generally, a foam head of less than 2 cm on a 60 square cm surface area is the upper limit of tolerance for commercial defoaming applications and for certain uses not more than 0.3 cm is required. Secondly, formulations containing these compounds are somewhat viscous which presents pumping difficulties in antifoaming processing. Several solid non-foaming dispersing formulations have also been proposed as in U.S. Pat. No. 3,959,176; however these present problems of dispersibility and cannot be pumped into foamable solutions.

Accordingly, it is an object of this invention to overcome the above deficiencies of the prior art and to provide a particularly effective antifoaming/defoaming mixture which is economically prepared.

Another object of this invention is to provide a liquid mixture which is capable of defoaming an aqueous system at a greatly increased rate.

Another object is to provide a liquid antifoaming/defoaming composition having significantly reduced viscosity which can be most economically incorporated into a foamable liquid or added to a foam.

Still another object is to prepare a composition which, in addition to its antifoaming and defoaming properties, provides antiswelling to various polymers when in contact therewith.

These and other objects of the invention will become apparent from the following description and disclosure.

In accordance with this invention there is provided a liquid antifoaming/defoaming mixture or blend of components having a cloud point less than 35 and comprising:

(a) between about 10 and about 90% by weight of a block polymer having the formula ##STR4## or mixtures thereof; (b) between about 10 and about 90% by weight of trimethylol propane initiated polypropylene oxide having the formula ##STR5## optionally in admixture with polypropylene glycol having the formula ##STR6## (c) between about 10 and about 90% of an alcohol alkoxylate having the formula ##STR7## to provide a 100% composition and (d) between about 0.1 and about 10% by weight hydrophobic silica based on components (a) +(b) +(c) wherein R is linear or branched chain alkyl having from 4 to 23 carbon atoms or a mixture thereof and the lettered subscripts have the following values:

the sum of a +c =10 to 150, preferably 20 to 70

b =2 to 100, preferably 4 to 30

d =0 to 100, preferably 0 to 50

e =20 to 150, preferably 30 to 100

f =15 to 200, preferably 25 to 100

g =1 to 20, preferably 4 to 15

h =0 to 15, preferably 0 to 10

the sum x +z =2 to 50, preferably 4 to 15

y =30 to 100, preferably 40 to 80

In the above, component (a) subscripts a, b and c as well as subscripts x, y and z, are integers having a value greater than one and describe a copolymer having a number average molecular weight of from about 675 to about 15,000, preferably from about 1000 to about 10,000. The units defined by (g) and (h) occur in random distribution in the copolymer.

The cloud point of instant mixtures can vary, from about 1 to about 35; although a cloud point of from about 1 to 25 is most beneficial.

Preferred blends of the present composition are those wherein the weight ratio of component (a) to component b) to component (c) are present in a weight ratio range of 0.3-3:1-6:0.3-2. Most preferred are those having a weight ratio of (a) to (b) between about 5:1 and 1:5, and those blends wherein propylene oxide units, with respect to ethylene oxide units, predominate in the overall composition.

The hydrophobic silica is preferably employed at concentrations between about 0.1 and about 10% by weight, most desirably, when a liquid mixture having a viscosity of not more than 500 centipoises (cps) is required, the concentration of the silica is not greater than 5% by weight. Although the viscosity of the liquid mixture can vary between about 100 and about 3,000 cps, depending upon its intended use, viscosities in the lower portion of this range, e.g. less than 550 cps, are usually desired for processing purposes. While increased hydrophobic silica content materially raises the viscosity, such increased amounts do not provide any antifoaming benefit. Accordingly, the amount of hydrophobic silica above 10% by weight is not desirable.

The hydrophobic silica component of the composition, as known in the art, is prepared from hydrophilic silica which is treated to render the silica hydrophobic. One suitable method for rendering the silica hydrophobic is to permanently affix a liquid hydrophobic polysiloxane oil onto the silica particles. Since hydrophobic silica is well known in the art, no detailed description thereof is deemed necessary for a complete understanding of the present invention. The preparation of hydrophobic silica is described in U.S. Pat. Nos. 3,207,698; 3,408,306; and 3,076,768, as well as the refeences referred to in such patents, all of which are hereby incorporated by reference. A preferred silica is a precipitated silica, such as the precipitated silica sold as QUSO-G30 or QUSO WR-83.

The above blend of components provides a hydrophobic/hydrophilic balance which allows faster diffusion of the antifoamer composition into the liquid/air interface and rapidly transports silica to the interface where a small amount efficiently performs defoaming action. The components of the above mixture also interact to effect destructurization of the monomolecular foamed layer by increasing the free energy of interaction between the foam forming molecules which leads to liberation of air and collapse of bubbles. Because of the hydrophobic/hydrophilic balance in the above formulation, the present composition has greater affinity for, and faster action in, aqueous systems which are subject to foaming. The present blend is capable of reducing the foam head of a foamed liquid by more than 70% upon contact and in less than 1.5 minutes completely destroys the foam.

In addition to its defoaming and antifoaming functions, the present composition provides antiswelling properties to certain polymers, including polyvinyl halides, polypropylenes, polyethylenes, polytetrafluoroethylenes, polychlorotrifluoroethylenes and the like.

Examples of foamed solutions to which the present composition is applied, include the alkali and alkaline earth metal salts, as well as ammonium salts, of alkyl benzene sulfonates and lauryl sulfates, lauryl ether sulfates, alkoxylated alkyl phenols, urethane polymers, phosphate ester surfactants, salts of fatty acids employed in the paper making industry and photopolymers, such as methacrylic alkyl esters and their carboxylic salts, employed for printed board circuits in the electronic industry. The present blends are useful as defoamers or antifoamers for laundry detergents, dishwashing formulations, paper making processes, metal working processes and many others.

To effect defoaming or antifoaming only a small amount of the blend is needed to provide the desired result. Generally between about 0.001% and about 3% by weight, preferably between about 0.05% and about 0.5% by weight of the present blend, based on foamed or foamable liquid, is employed to defoam on contact. The present mixture is economically and conveniently prepared by merely mixing components (a), (b) and (c) in any order at a temperature between about 10° C. and about 100° C. under atmospheric conditions for a period of up to 3 hours depending upon the volume and mixing equipment employed. Generally, the formulation is prepared within a 1 hour mixing period at ambient temperature. The resulting mixture is preferably used in undiluted condition; although in certain cases where desired, it can be diluted to a desired concentration with an inert solvent such as water, PEG, PPG, benzene, heptane, hydrocarbons and the like before contact with a foamed layer or before admixture with a foamable liquid prior to agitation. The defoaming or antifoaming operations are carried out under the same conditions of temperature and pressure described above using conventional foam breaking or liquid mixing techniques.

Having generally described the invention, reference is now had to the accompanying examples which include preferred embodiments. These examples are not to be construed as limiting to the scope of the present antifoaming/defoaming and anti-swelling compositions which are more broadly set forth above and in the appended claims.